Patent GB-1120788-A (GB)
Title: Valve assemblies for controlling fluid motors
IPC: F16K11/07
Filed: 1965-10-25
Abstract: 1,120,788. Valves. PARKER-HANNIFIN CORP. 25 Oct., 1965 [12 Nov., 19641, No. 45115/65. Heading F2V. [Also in Divisions F1 and G3] When a pair of spool valves 18, 19, Fig. 3, are in the locked neutral - position shown, the supply port 7 is open to a tank port 9 via by-pass passages 23, 24, 25 which intersect the spool valve bores 16, 17; the latter are also intersected by pressure passages 26, 27 and motor passages 31, 32 respectively and common return passages 34. The pressure passages 26, lead to the supply port through a chamber 28 and a trunk passage 28<SP>1</SP>, Fig. 6, via check valves 29 in a bore 81 parallel to bore 16. Check valves 30, Fig. 3, of a spool 19 are disposed in the ends of the latter. The return passages 34 communicate with the port 9 through a flow control valve 36, and with the chamber 28 by a passage 37, a check valve (38, Fig. 4, not shown) and passage 28<SP>1</SP>. A principal pilot-valve actuated relief-valve 40 is disposed between the passage 28<SP>1</SP> and the port 9, Fig. 3, whilst the valve 36 consists of a fixed sleeve 50 open to the by-pass passages 25 and embodying openings 53 controlled by a slidable sleeve 54 having ports 59 and a loading spring 56. Upon actuation of one or both spools the pressure in passage 281 which is open to a chamber 57 causes movement of the sleeve and alignment of ports 53, 59. Should cavitation occur then the pressure in the chambers 28, 57 will fall and valve 36 will close; when the pressure in the return passages then increases to a level where it exceeds the inlet pressure, the check valve 38 is opened so that the exhaust fluid is returned to the motor to supplement the pump output. Parallel to bore 17 is another bore 60, Fig. 5, into which open the motor and return passages 32, 34 and the trunk passage 28<SP>1</SP> each end of the bore housing a pilot-controlled main relief valve. A high pressure in one motor passage 32 resulting from returning the spool 19 to neutral acts in the associated pilot relief-valve 70 via an orifice 73 in the related main valve 65 to open the valve 70 and exhaust the pressure in a chamber 74 so that the high pressure can then open the main valve 65 whereupon fluid traverses a tube 72 to open directly the other main valve 65 in the manner of a check valve and interconnect the motor passages 32 and prevent cavitation. The bore 81, Fig 6, may embody a relief valve 86 at one or both ends to cater for any over-pressure resulting from moving the spool 18 from an operating to the neutral position. The check valves 29, 30 may be resited in the bore 60, Fig 5, around the tube 72 between the passage 28<SP>1</SP> and each pressure passage 27. If the passage 28<SP>1</SP> does not extend into bore 60 and one or both blanking-off tubes 62 are shortened to enable the by-pass passage 25 to open into the bore 60 then only one motor at a time may be operated. The principal pilot-actuated relief-valve may also be arranged to function as a check valve which prevents cavitation in association with valve 36 by directing excess pressure fluid returning from the motor to the inlet chamber 28; the fluid in the return passages acts directly on the main relief valve.